The present invention relates to a loop bus priority control method for use in a network in which a plurality of processors are connected through a uni-directional loop bus.
In the conventional loop bus network in which a plurality of host processors are connected by a unidirectional loop bus through node processors, in order to shorten the data transmission delay time, there is often adopted a through-communication method where data passed through without processing. In accordance with this method, since the bus is theoretically treated as one common bus, when a plurality of host processors simultaneously require data transmission, a contention for use of the bus may occur. Accordingly, permission for use of the bus must be given to the host processors in some orderly manner which will avoid such contention.
For this purpose, there has heretofore been a central control system in which a processor for use exclusively in controlling the bus is formed in the loop and this processor performs the control necessary to properly allocate use of the bus. However, according to this known system, the required control is very difficult and high speed transmission is difficult to achieve. Furthermore, if trouble or disorder occurs with this bus control processor, the entire system will not function at all.